diff options
Diffstat (limited to 'src/include/nodes/relation.h')
| -rw-r--r-- | src/include/nodes/relation.h | 20 |
1 files changed, 16 insertions, 4 deletions
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h index 59f83e8562..d54770eabc 100644 --- a/src/include/nodes/relation.h +++ b/src/include/nodes/relation.h @@ -7,7 +7,7 @@ * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.178 2009/10/26 02:26:43 tgl Exp $ + * $PostgreSQL: pgsql/src/include/nodes/relation.h,v 1.179 2009/11/15 02:45:35 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -835,6 +835,14 @@ typedef JoinPath NestPath; /* * A mergejoin path has these fields. * + * Unlike other path types, a MergePath node doesn't represent just a single + * run-time plan node: it can represent up to four. Aside from the MergeJoin + * node itself, there can be a Sort node for the outer input, a Sort node + * for the inner input, and/or a Material node for the inner input. We could + * represent these nodes by separate path nodes, but considering how many + * different merge paths are investigated during a complex join problem, + * it seems better to avoid unnecessary palloc overhead. + * * path_mergeclauses lists the clauses (in the form of RestrictInfos) * that will be used in the merge. * @@ -846,15 +854,19 @@ typedef JoinPath NestPath; * outersortkeys (resp. innersortkeys) is NIL if the outer path * (resp. inner path) is already ordered appropriately for the * mergejoin. If it is not NIL then it is a PathKeys list describing - * the ordering that must be created by an explicit sort step. + * the ordering that must be created by an explicit Sort node. + * + * materialize_inner is TRUE if a Material node should be placed atop the + * inner input. This may appear with or without an inner Sort step. */ typedef struct MergePath { JoinPath jpath; List *path_mergeclauses; /* join clauses to be used for merge */ - List *outersortkeys; /* keys for explicit sort, if any */ - List *innersortkeys; /* keys for explicit sort, if any */ + List *outersortkeys; /* keys for explicit sort, if any */ + List *innersortkeys; /* keys for explicit sort, if any */ + bool materialize_inner; /* add Materialize to inner? */ } MergePath; /* |